1. Field of the Invention
The present invention relates to a solid-state image sensor and an imaging system having the solid-state image sensor and, more particularly, to the pixel structure of the solid-state image sensor.
2. Description of the Related Art
As solid-state image sensors used in imaging systems such as a digital camera and camcorder are gaining smaller sizes and more pixels, the pixel size shrinks rapidly. A smaller pixel size leads to a smaller area of the light receiving portion of a photoelectric conversion element in the pixel, decreasing the sensitivity of the photoelectric conversion element. To suppress the decrease in the sensitivity of the photoelectric conversion element, a technique of forming an on-chip microlens on the light incident surface of a pixel has already been in practical use. Recently in some arrangements, a light waveguide is formed between a microlens and a photoelectric conversion element to collect light using total reflection of light. Japanese Patent Laid-Open No. 2007-201091 discloses a structure in which a light waveguide is formed by filling a through hole 41 formed in a planarizing layer with a high-refractive-index material, and covering the upper surface of the planarizing layer with a high-refractive-index material.
However, in the structure disclosed in Japanese Patent Laid-Open No. 2007-201091, light propagates while being reflected by the upper and lower surfaces of the high-refractive-index material layer arranged on the planarizing layer between adjacent light waveguides. As a result, light may enter the light waveguide and further the photoelectric conversion element. This may cause mixture of colors or a noise component.